diff --git a/src/AmqpConnectionManager.re b/src/AmqpConnectionManager.re
index f78aafa..69bf7b6 100644
--- a/src/AmqpConnectionManager.re
+++ b/src/AmqpConnectionManager.re
@@ -82,7 +82,7 @@ module ChannelWrapper = {
 
   [@bs.send]
   external publish':
-    (t, Exchange.name, routingKey, Js.Json.t, Js.t('options)) =>
+    (t, Exchange.name, routingKey, 'message, Js.t('options)) =>
     Js.Promise.t(unit) =
     "publish";
 
@@ -91,7 +91,7 @@ module ChannelWrapper = {
 
   [@bs.send]
   external sendToQueue':
-    (t, Queue.name, Js.Json.t, Js.t('options)) => Js.Promise.t(unit) =
+    (t, Queue.name, 'message, Js.t('options)) => Js.Promise.t(unit) =
     "sendToQueue";
 
   let sendToQueue = (t, q, m, o) =>
diff --git a/src/AmqpConnectionManager.rei b/src/AmqpConnectionManager.rei
index c100423..fb21d8c 100644
--- a/src/AmqpConnectionManager.rei
+++ b/src/AmqpConnectionManager.rei
@@ -63,11 +63,11 @@ module ChannelWrapper: {
     t;
 
   let publish:
-    (t, Exchange.name, routingKey, Js.Json.t, Js.t('options)) =>
-    Js.Promise.t(Js.Json.t);
+    (t, Exchange.name, routingKey, 'message, Js.t('options)) =>
+    Js.Promise.t('message);
 
   let sendToQueue:
-    (t, Queue.name, Js.Json.t, Js.t('options)) => Js.Promise.t(Js.Json.t);
+    (t, Queue.name, 'message, Js.t('options)) => Js.Promise.t('message);
 };
 
 module AmqpConnectionManager: {